The present invention relates to a load selector, in particular for an exercise machine that allows a variation of the resistance offered to the user thanks to a corresponding variation of the load related to a certain exercise.
Numerous physical fitness or rehabilitation exercises entail the use of a load to provide a reaction to the force imparted by the user.
Currently, "traditional" weight training, such as dumb-bells, bars and the like, have been, to a great extent, replaced by exercise machines that are more complex and correlated to their use, indicated as isotonic machines. Such machines comprise a base frame whereto are associated means for the user to impart a force, such as a bar, handles or oar-shaped levers, connected to a load which provides a resistance to the imparted force. The load, gravitational, is defined by the weight of a series of brick- or disk-shaped weights, able to be placed in different mutual association according to the exercise to be performed until reaching the desired weight value. The connection between the means for imparting the force and the load is constituted by a cable or by a chain wound around transmission pulleys or through a lever system directly associated to the load and to the means for imparting the force.
In practice, according to the most widely used embodiment, an exercise machine comprises a metal structure provided with a seat for the user (when necessary, of course) and a vertical guide destined to allow sliding by a series of weights connected, through the aforesaid chain or cable, to a bar (or other element for the application of force) which is gripped by the user to perform work generated by lifting the weights, thereby sliding them along the guide.
A drawback of the machine currently in use derives from the ways whereby the working load is determined, i.e. by the manner in which the weights are associated to the chain or to the cable. Each weight can slide along the aforesaid vertical guide and it presents at least one vertical through hole and one horizontal through hole mutually intersecting; the superposition of the weights determines, in correspondence with the vertical holes, a sliding channel for a connecting rod positioned vertically and connected, in its upper end, to the chain; the selection of the load for the exercise to be performed is made manually by inserting a locking pin, passing through one of the horizontal holes presented by the weights, into one of the seats provided on the rod at different heights corresponding to the thickness of the weights. In this manner, all the weights located above the inserted pin are associated with the rod, and hence with the chain; by varying the insertion height, the number of weights associated with the chain and, hence, the load for the exercise is varied.
When, on the same machine, a series of exercises requiring different loads is to be performed (for instance, in passing from a series to the next one), or when the same machine is used by multiple persons alternating with different loads, it is necessary, for each change, to set the machine up, removing the locking pin and inserting it at a different height; such operation is found annoying, especially if one considers that gymnasium activities generally have a recreational and entertainment character. Among prior art solutions, U.S. Pat. No. 4,834,365 is related to a combined system of weights, with which it is possible to select, for the same weight stack, weights of different values.
U.S. Pat. No. 4,971,305 relates to a device that allows adjusting the weight stack having variable values, i.e. on values corresponding to sub-multiples of the unit of measure, with increments of small value. With the aforesaid solutions it is not possible to vary automatically (i.e. not manually) the reaction provided by the machine.
U.S. Pat. No. 5,556,362 relates to a pin for weights able to disengage automatically when the weight stack reaches the rest position. The subject pin can be used to deselect one or more weight bars, but it is not usable to set the load of a given exercise or to increase the load itself.
U.S. Pat. No. 4,610,449 relates to an automatic weight selector which automatically changes the selected weight after a set time interval. The patent describes a structure that fastens a plurality of bars to the tugging rod, through two pins, a lower one and an upper one, inserted in respective seats presented by two weight bars; load differentiation is allowed by a cam device commanded by a timer which, after a set period of time, extracts the lower pin to lighten the load, maintaining, connected to the rod, the above-lying bar and those above it. With the selector, thus described, it is therefore possible to change load by decreasing it and only once, in the course of a break.
U.S. Pat. Nos. 4,746,113 and 5,350,344 relate to exercise machines, wherein the load of the weight stack can be varied. Both documents teach the use of a structure able to be combined to a weight stack and supporting a series of pins movable horizontally between an engaged position wherein they are inserted in the related seats of the weight bars and a release position wherein they are retracted from the seats thereby freeing the weight bars. In practice, it is a sort of plate presenting pins facing the weight stack and able to be activated, by means of solenoids or electromagnetic actuators provided and acting upon each of the aforesaid pins. The solutions taught in the two patents provide for a structure which must follow the weight stack in its vertical stroke.
U.S. Pat. No. 4,546,971 describes an exercise machine wherein the load of the weight stack can be varied through a lever positioned in proximity to the seat destined for the user. The weight bars used in this solution are fitted with a pin passing through the horizontal seat which allows access to the tugging rod of the weight stack. Each pin presents spring means which thrust it towards the outside of the weight bar, in a disengagement position from the tugging rod, and it is fitted with an outward projecting head. The aforementioned lever is connected to a command rod able to slide vertically, provided with cams destined to interact with the heads presented by the pins, thereby thrusting the pins towards the tugging rod, in a number corresponding to the desired load value.